straight pull twistgrip

[philip.butcher]

i have found an amal straight pull twistgrip which i believe was used on square four models in the late fiftys?
does any body recognise and know what models it was fitted to and when?
presumably it was used on other makes as well?
thanks in advance philip

[Cas.vanderwoude]

I'm looking for one or more of these if any members have one to sell...